Cartridge-type staplers for staple binding are known, in which a cartridge accommodating therein a multiplicity of straight non-formed staples is mounted to a magazine of an electrically driven stapler, non-formed staples in the cartridge are sequentially supplied to a striking part formed on a tip end of the cartridge, the non-formed staple is formed just this side of the striking part by a forming plate to be C-shaped, and the formed staple is supplied into a striking passage, in which a driver plate slides, the driver plate strikes out the formed staple from the striking passage so as to penetrate the staple legs through sheets arranged on a lower surface of the cartridge.
The cartridge accommodating therein a multiplicity of staples is formed at a tip end thereof with the striking passage for striking-out of a single leading staple toward the sheets, and the striking passage is formed between a front end surface of the cartridge and a face plate mounted to a front end of the cartridge. The driver plate reciprocated and driven by a motor provided on a body side of the electrically driven stapler enters into the striking passage formed at the front end of the cartridge to strike out a staple arranged in the striking passage, and tip ends of staple legs penetrating through the sheets disposed on a lower surface side of the cartridge are bent by the clincher mechanism.
With conventional, electrically driven staplers, an anvil arranged on a lower surface of a non-formed staple is formed just this side of a striking passage, the anvil and a forming plate form the non-formed staple to make-the same C-shaped, and the C-shaped staple is supplied into the striking passage by a pusher arranged below the anvil. When a non-formed staple is formed by the forming plate to be C-shape, the pusher is retreated to engage with a rear surface side of the staple, which is formed to be made C-shaped, to push the formed staple forward with a spring bias to supply into a groove of a face plate that defines the striking passage. When a staple in the striking passage is struck out by the driver plate, the pusher pushes staple legs from rear surface sides thereof so as to guide the staple legs struck out.
Forming of a non-formed staple is begun by the forming plate and staple legs in the course of forming abut against the pusher whereby the pusher is retreated to engage with a rear surface side of the C-shaped staple so as to push the staple toward the striking passage. When the pusher is retreated, a pushing force that pushes the staple arranged in the striking passage from the rear may disappear, and guiding may not be sufficiently performed in some cases. In the case where the staple legs of the formed staple are large in length, a large penetrating resistance is generated until tip ends of staple legs penetrate through the sheets, after a crown portion is pushed by the driver plate and the tip ends of the staple legs struck out touch a surface of the sheets. When a pushing force from the rear disappears as described above due to a large distance between the driver plate and the tip ends of the staple legs, jam of staple legs is liable to generate. This tendency is remarkable specifically in a stapler, in which a dimension between tip ends of staple legs and the sheets is set to be large.
As described above, as a technique for guiding of staple legs struck out in a stapler, in which a dimension between tip ends of staple legs and sheets is set to be large, it is known that guide grooves for guiding of front and rear surfaces and both right and left side surfaces of a formed staple are formed integrally on a face plate that defines a striking passage, and a staple formed by a forming plate is fed into the guide grooves by a driver plate, and further struck out toward the sheets from the guide grooves by the driver plate (see, for example, JP-Y2-2501487).
In such conventional electrically driven stapler, there is a need for mechanisms such as a spring that supports the face plate vertically movably and biases the face plate upward, a supporter for prevention of falling of a staple in the guide grooves formed on the face plate, etc., which make the mechanisms complex and a cause for an increase in cost of the electrically driven stapler. Also, conventional mechanisms are set so that the driver plate strikes out a formed staple at the same time the forming plate forms a non-formed staple to make the same C-shaped, and forming by the forming plate is begun to retreat the pusher before a staple struck out has penetrated completely through the sheet, so that a rear surface of the staple struck out is not supported and an unstable striking state is brought about, which makes a cause for failure, such as jam, etc., in striking.